As a consequence of an ischemic myocardial event, blood supply distal to an arterial occlusion is significantly diminished. The resulting deprivation of oxygen places this tissue at risk of necrosis. The standard of care for ischemic events is urgent revascularization of the occluded artery, which is commonly performed by minimally invasive catheterization followed by angioplasty, in order dilate the ischemic blockage and fully restore the supply of the blood to the tissue.
However, restoration of blood to the tissue can result in a cascade of metabolic and inflammatory responses which can lead to the necrosis of potentially salvageable myocardium despite the restitution of adequate blood supply. This reperfusion injury significantly extends the size of the infarct, and leads to increased morbidity and mortality. A possible way to avoid this reperfusion injury is to control the flow of blood to the distal tissue following reperfusion, which may mitigate the metabolic and inflammatory response of ischemic issue when being reperfused. This may be accomplished by initially crossing the ischemic occlusion with a guidewire. A balloon or stent delivery system is then delivered across the occlusion the guidewire. The balloon or stent is deployed to dilate the vessel occlusion and restore the blood flow to the distal vessel. However, rather than maintaining the blood flow in a constant manner, it is contemplated that a more efficacious approach is to restore the blood in an intermittent fashion. In this way, the reperfused tissue will be oxygenated gradually, which will mitigate the deleterious effects of reperfusion. This will in turn maximize the tissue viability post-procedurally.
In addition, after deployment of a stent or balloon within the ischemic region, there may be thrombus generated, which is released into the blood stream. Generally, the thrombus will be carried to a distal region of the vasculature, but in some cases it may remain near the lesion or in a location that is proximal to a vessel bifurcation that supplies significant blood to heart tissue. When the thrombus remains in a more proximal location within the vessel, it presents an increased probabilistic risk of occluding the vessel and forming another ischemic event. This risk can be mitigated by displacing the thrombus to more and more distal regions of the vasculature, so that when it does occlude a vessel it will generally be a much smaller vessel that is less significant in terms of maintaining tissue viability.
Therefore, there exists a need for medical devices that are capable restoring blood flow after an ischemic in an intermittent and gradual fashion. In addition, there also exists a need for medical devices that are capable of forcing thrombotic particles into more distal regions of the vasculature to avoid ischemic events that compromise large areas of cardiac tissue.